If you wear boots (particularly full-leather), the following is a great combination for comfort and to eliminate blisters.
For the inner layer, use the new injinji performance toe sock. These a like a second skin and a great smooth interface for your feet. The individual sections for your toes prevent friction. This is very effective. A thin liner like this prevents the friction from coarser threads in most bushwalking socks. These are totally synthetic and moisture wicking.
For the outer layer I use the thickest sock I can find. The macpac winter hiker. These are a Luxurious merino-based sock that are very comfy. They provide great padding for your feet. One thing to be careful about is to avoid putting the socks in the wash with anything that has Velcro. The socks will get caught and sections of the very fine fibres will be damaged. It's minor damage and won't be a major problem as they are a thick sock. I will be more careful with future washes.
NB: no affiliation with either product